1. Field of the Invention
The present invention relates to a substrate processing apparatus and method for performing a designated process, such as a cleaning process, drying process, and an etching process, for processing a substrate, such as a semiconductor wafer or a glass substrate for a LCD (liquid crystal display), by using a pressurized fluid, such as a supercritical fluid.
2. Description of the Related Art
Generally, semiconductor device fabricating processes include processes for forming films, such as photoresist films, on semiconductor wafers and processes for removing the films from the wafers.
Use of large-diameter wafers and the reduction of minimum line width are the recent trend of semiconductor device fabricating technology to reduce the manufacturing cost of chips. The price of semiconductor memories, such as DRAMs, has sharply dropped in recent years, and semiconductor device manufacturers, principally of advanced countries, have been shifting to the manufacture of products having higher added values, such as system LSICs. There has been a trend for semiconductor device manufacturers to prefer small-scale multiple-product production to mass production with the change from the production semiconductor devices with low added values to the production of those with high added values. Problems relating to EHS (environment, health and safety) have become important problems to be tackled by the semiconductor device industry. Reduction of injurious industrial wastes and power consumption has become a problem of the utmost importance to be solved by the semiconductor device industry.
The required abilities of semiconductor device fabricating systems and processes have greatly been changing, reflecting such a recent trend of the semiconductor device industry. Semiconductor device fabricating systems are being changed from those of a batch processing system to those of a single-wafer processing system to cope with necessity for wider floor space resulting from the progressively increasing use of large-diameter wafers, to improve the throughput of small-scale multiple-product production systems and to raise device yield. The single-wafer processing system is capable of uniform processing and precision process control. The single-wafer processing system adopts process integration to exclude the effect of external disturbances. Research and development are being made actively for the development of processes to deal with new semiconductor device materials, such as copper and insulating materials having a low dielectric constant, as process technology of the next generation to cope with the progressive reduction of line width.
Although abilities as mentioned above have become important for cleaning apparatuses and resist coating/developing apparatuses, the development of processes that replace wet processes and the reduction of the necessary quantity of volatile organic substances and chemicals are significant problems from the viewpoint of EHS and the process technology of the next generation. Cleaning, drying and etching processes and apparatuses using a supercritical fluid, such as carbon dioxide (CO2) are particularly promising techniques among those recently developed to solve the foregoing problems. Process techniques using a supercritical fluid have become prevalently used in various industries, the effectiveness of supercritical fluids have become widely known. The earth has virtually inexhaustible carbon dioxide, and carbon dioxide is a low-cost industrial material and is a highly safe, harmless, inactive substance. Research and development activities, which have been made up to the present, emphasize the following advantages of supercritical fluids.
1) Properties of supercritical fluid characterized by a surface tension of zero, a density nearly equal to those of liquids and a viscosity nearly equal to those of gases are very effective in processing minute patterns.
2) The solubility of supercritical fluids in organic materials can be greatly increased by using a small amount of solvent with supercritical fluids, which is effective in removing photoresist films and cleaning off residuals.
3) A dissolved substance diffuses at a high diffusion rate and hence uniform processing can be achieved.
4) Supercritical fluids react scarcely with metals, and hence do not damage wiring materials and barrier metals.
5) Supercritical fluids can be discharged from a processing vessel in a gas before taking out a wafer from the processing vessel and hence a drying process is unnecessary.
A supercritical-fluid system using a supercritical fluid for substrate processing is disclosed in Japanese patent laid-open publication Nos. JP 11-87306A. This known supercritical-fluid system supplies a supercritical fluid into a processing vessel accommodating a wafer holding means holding a wafer and capable of rotating the wafer to process the wafer for cleaning, etching and drying. Another substrate processing system, using a supercritical fluid, disclosed in Japanese patent laid-open publication Nos. JP 2001-60575A has a heater embedded in a casing surrounding a processing vessel and heats the processing vessel to control the temperature of the supercritical fluid. Another substrate processing system disclosed in Japanese patent laid-open publication Nos. JP 2001-327936A has a processing vessel provided with a circulation pipe, a fluid is circulated through the circulation pipe by a pump and is heated in a supercritical state by an external heater.
The supercritical-fluid system disclosed in JP 11-87306A has a motor for rotating the substrate holding means, which is disposed outside the processing vessel. Since the high-pressure supercritical fluid is supplied into the processing vessel, the joint of the substrate holding means and the motor in the processing vessel must be provided with a special sealing device, which increases the size of the supercritical-fluid system. Since the wafer is subjected to a cleaning process by rotating the wafer in the processing vessel filled up with a supercritical fluid or a supercritical fluid containing a chemical, particles and organic contaminants adhering to the wafer cannot satisfactorily be removed.
The substrate processing systems disclosed in JP 2001-60575A and JP 2001-327936A have complicated construction because the heater is embedded in the casing surrounding the processing vessel or the pump and the external heater are combined with a circulation pipe disposed outside the processing vessel.